Very craters in Greenland are much older than scientists thought
The one-kilometer meteorite traffic a few million years after the dinosaurs died out.
In 2018, a team led by Danish researchers will publish an exciting discovery. They had discovered a huge crater that was hiding under the ice in Greenland.
The crater is 31 kilometers wide and was made of an iron asteroid of one kilometer that narrowed to the ground. It is called the Hiawatha Crater, after the name of the glacier that covers it.
The researchers studied the crater and the structure of the ice with radar measurements. Based on this, at first it seemed that the crater was quite young.
They came to the conclusion that the impact happened after they began to settle in Greenland, ie not earlier three million years ago and perhaps as sent as 12,000 years ago. Some have wondered whether the impact affected the climate at the end of the ice age.
However, a new study shows that the crater is much older.
The asteroid hit 58 million years ago, eight million years after the dinosaur was exterminated by a at least twice as large asteroid.
Excludes hits at the end of the ice age
The journal Science writes that the new studies are a setback for a controversial hypothesis called Younger Dryas impact hypothesis. It states that a comet hit the earth 12,800 years ago, causing climate change and extinction.
Younger dryas are one of several cold spells that interrupted the otherwise gradual warming after the last ice age maximum.
The crater in Greenland has been mentioned as a possible crime scene that can pass with this hypothesis, such as in this article from 2019 in scientific reports.
Now it is clear that the meteorite impact happened at a completely different time in the earth’s history.
Warm climate
Two laboratories in Sweden and Denmark have used different methods to date the crater. Both methods gave about the same result: The crater is 58 million years old.
At this time there were no glaciers in Greenland.
The temperature was around 20 degrees. In the Arctic, there was temperate rainforest and bustling wildlife, according to a press release from the University of Copenhagen.
The one-kilometer asteroid probably did great damage in the area.
If a lump of stone on this size traffic Europe today, it would be led to great destruction in an area the size of France and had effects throughout Europe. Crater expert Henning Dypvik told forskning.no recently.
Fires, earthquakes, dust and rocks that spread over large areas, as well as pressure waves such as more down trees are some of the effects.
Global impact?
So far, there is no evidence that the impact had any impact on the global climate 58 million years ago, or that it led to extinction. This is something the researchers want to investigate further.
– Our next step is to investigate geological sections from the Paleocene that are 58 million years old to see if we can identify a signal from the impact, says Nicolaj Krog Larsen, professor at GLOBE Institute at the University of Copenhagen to Gizmodo.
– This is important if we want to understand whether a downpour of this magnitude changed the climate on earth or led to any mass extinction, something we doubt it did.
So far, only the meteorite that exterminated the dinosaurs 66 million years ago has been shown to have global consequences for life on Earth. It was over ten kilometers large.
Sand and gravel
The new dating is based on rocks and sand at the foot of the glacier. Some of the material has been transported out with meltwater from the crater. Here the researchers found stones that were exposed to strong heat.
The researchers used radiological dating to find out when the stone was altered by the impact. One way to find out how old a rock is is to look at how much uranium and lead there is in it. Radioactive uranium is slowly but surely converted to lead at a steady pace.
Rock samples from the foot of the Hiawatha Glacier were sent to the Swedish Museum of Natural History. The researchers studied small crystals of the mineral zircon in the stone, writes Science.
Some of the zircon crystals were “shocked”. This means that it was characteristic fractures in the crystals that can be seen where large meteorites have crashed. The impact knocked out impurities of lead in the crystals. Thus, the uranium clock was set again, explains Science.
At the Statens Naturhistoriske Museum in Denmark, researchers used a different method. They analyzed sand grains from the same site by looking at the degradation of radioactive potassium to argon.
– Convinced
Researchers feel confident that the new dating is right.
– Dating the crater has been a particularly tough nut to crack, so it is very satisfying that laboratories in Denmark and Sweden, which use different dating methods, came to the same conclusion, says Michael Storey at the Statens Naturhistoriske Museum in Denmark in the press release.
– Therefore, I am convinced that we have found the right age on the crater, which is much older than many previously thought.
Researchers which Videnskab.dk has spoken to is the only one in that the new dating looks real.
Several craters may be hiding under the Greenland ice sheet. In 2019, scientists discovered another possible crater in Greenland with radar.
References:
Gavin G. Kenny, et al .: «A late Paleocene age for Greenland’s Hiawatha impact structure», The progress of scienceMarch 9, 2022
KH Kjær and others: «A large impact crater under the Hiawatha Glacier in northwestern Greenland», The progress of science (2018), DOI: 10.1126 / sciadv.aar8173
Article in CORDIS EU research results: Atomic walls made of crushed zircon crystals can date asteroid impacts